This invention relates generally to manually compressible foam dispensers and particularly to dispensers having a rigid foam producing porous member.
The production of foam from flexible containers providing a deformable reservoir containing liquid and air which are intermixed prior to discharge is well known. Such foam dispensers provide an alternative to the well-known rigid type of container from which foam is dispensed under pressure by means of a compressed gas propellant. The rigid type of container is effective for its intended dispensing purpose but suffers from several serious objections. One of these is the high cost of the container which must be formed of a metal strong enough to withstand the internal gas pressure. Another objection results from the undersirability of expelling the fluorocarbon type of propellant commonly used into the atmosphere, as the release of such products creates potential ecological as well as health hazards, and further, this type of device is subject to explosion under some circumstances and therefore constitutes a safety hazard also. In addition to these objections, the pressurized type of device suffers from the disadvantage that the foam-forming gas used is not self-replenishing, thus limiting the useful life of the dispensing device.
The production of foam having optimum characteristics with respect to spreading, stability and wetting properties is dependent not only on the foamable liquid used but also on the means used to produce the foam. In general, the known non-pressurized, flexible container dispensers, utilize sponge-like porous elements of resilient material such as urethane foam, natural sponges and the like. Resilient material of this sort suffers from the inherent disadvantage that compression creates an undesirable change in porosity. A further disadvantage is that resilient materials of this sort are not self-supporting. Examples are disclosed in the patents issued to Stossel, U.S. Pat. No. 3,010,613; V. M. Bruno, U.S. Pat. No. 3,308,993; and A. L. Boehm et al., U.S. Pat. No. 3,422,993. Of these, the Boehm patent is believed to be the most pertinent. However, the porous member employed in this device is not self-supporting but requires a rigid inner holder mounted within the container to support the porous member. In addition, the area of the porous member exposed within the container is strictly limited and the exposure of the porous material to the fluid is indirect rather than direct. Further, the dip tube of the Boehm device does not extend into the porous member and there is a tendency for air and liquid to pass through the porous member without foaming.
It is also known that devices utilizing resilient porous material are incapable of passing granular materials such as finely ground pumice stone, polyethylene or silica, which is suspended in the liquid, without clogging the porous material.
The present device solves the above and other problems in a manner not disclosed in the known prior art.